The Flu Shot Conundrum: Timing and Effectiveness Matter

As the annual flu season approaches, the debate on when to receive the flu shot has sparked a discussion on the effectiveness of the vaccine and the timing of vaccinations. Research suggests that flu shot effectiveness wanes significantly over time, just like Covid-19 shots, particularly in high-risk individuals. This has led to a question: why do public health officials recommend getting vaccinated as early as September, when antibodies are still rising, while high-risk individuals may benefit from delayed vaccinations?

Key Takeaways:

• A substantial body of research indicates that flu shot effectiveness wanes over time, particularly in high-risk individuals, with antibodies reaching their highest levels just a few weeks after vaccination.
• Tens of millions of Americans have received their annual flu shots, but the Centers for Disease Control and Prevention (C.D.C.) has not recommended delaying the vaccine campaign to allow for more effective protection during the winter months.
• Epidemiologists at the C.D.C. focus on vaccine uptake, rather than the percentage of severe illnesses averted, which may conflict with one another.
• A model suggests that starting the annual vaccine campaign in October rather than September could reduce flu-related hospitalizations by 3 or 4 percent, potentially resulting in up to 10,000 fewer hospitalizations.
• The C.D.C. has opted not to delay the flu shot campaign, but a solution could be to start vaccinations in October instead of September.
• The National Institutes of Health and other researchers should study the effectiveness of a two-dose flu vaccine for high-risk populations, like seniors and the immunocompromised, which would provide better protection throughout the flu season.
• Scientists have previously tested two-dose versions of the flu vaccine but with the wrong regimens, and a second dose given a few months after the first one may provide more protection and prevent more hospitalizations.

Statistics:

• By the end of October, a quarter of seniors in the United States have received their annual flu shots.
• Last year, weekly flu-related hospitalizations were over 44 times higher at their eventual peak in late December than they were in the first week of October.
• This year's flu shot was 35 percent effective at preventing hospitalizations in the Southern Hemisphere, with effectiveness varying by age and other risk factors.
• Effectiveness was 31 percent in older people and 59 percent effective for young adults with medical comorbidities.
• Up to 10,000 fewer hospitalizations could be prevented by delaying the vaccine campaign to start in October rather than September.

Sources:

• National Institutes of Health
• Centers for Disease Control and Prevention (C.D.C.)
• Southern Hemisphere flu season data (year not specified)
• Jeremy Faust, doctor in the emergency medicine department at Brigham and Women's Hospital (article author)
• The New York Times (original article)